Paper holder, drive take-up apparatus



Oct. 15, 1963 B G, PRICE ETAL 3,107,064

PAPER HOLDER, DRIVE TAKE-UP APPARATUS Filed Nov. l5, 1961 5 Sheets-Sheet 1 Z INVENTUM f BY mJy/@Imm Oct. l5, 1963 B. G. PRICE ETAL PAPER HOLDER, DRIVE TAKE-UP APPARATUS 3 Sheets-Sheet 2 Filed NOV. 13, 1961 9 o@ ao A# WM Aca 0 M/ml (#4 f O .i -fw mn wfg o N,.|| l|ii .W W 6 f i 5 L?. iw i? J0 f n -T if i. wmJi ...HHHHHHHHHNH w w, wljillwl I 7% 4,- :MH P- m- N -xm Z A- 3 7 L S 10 a 0 Z 2\ 4^ a 3 f m Oct. 15, 1963 B. G. PRICE ETAL PAPER HOLDER, DRIVE TAKE-UP APPARATUS 5 Sheets-Sheet 3 Filed NOV. l5, 1961 e/M @Aam cec/m W f 1 @n i@ m e@ E w @wm 55C M w M/ ATTO/PNEYJ United States Patent O 3,107,064 PAPER HOLDER, DRIVE TAKE-UP APPARATUS Berry G. Price, Eugene A. Placke, and Claude D. Stegall,

all of Houston, Tex., assignors to Tuboscope Colnpany, Harris County, Tex., a corporation of Texas Filed Nov. 13, 1961, Ser. No. 151,907 4 Claims. (Cl. 242-55) This invention relates to the devices for recording electrical signals and other variables with respect to time. In particular, the invention concerns the drive mechanism for drawing a record-ing sheet from a roll past the writing head of a recorder in a uniform manner and at a constant speed.

The sheet drive mechanism of a recorder is the heart of the dew'ce as it controls the speed and deployment of the sheet. The sheet speed should be constant and the sheet should always be 'flat as it passes the writing head. When slack occurs between the sheet roll and the drive mechanism some recorders vary the speed of the sheet to take-up the slack. And, in many cases, the slack causes the sheet to pile-up adjacent the writing head. Another diculty is encountered in driving mechanisms when the driving for-ce -on the sheet is not uniform all along the sheet surface. The sheet tears or folds under the writing head if the driving force is different along the sheet surface and serious stoppages result.

The present invention is concerned with eliminating the disadvantages set forth above and in a unique and novel way has achieved a recording mechanism where the sheet is driven with minimum slippage and by a constant and uniform driving force as the sheet passes under the writing head.

It is therefore an object of the present invention to have a recording mechanism with a paper drive that Substantially eliminates the effect of slack occurring between the sheet mechanism and the sheet roll.

It is further an object of the present invention to provide a uniform driving fonce for the sheet as it passes adjacent the writing head.

It is still another object of the present invention to provide a sheet drive mechanism in combination with a sheet roll holder to automatically take-up any slack occurring between the drive shaft and the sheet roll without changing the speed that the sheet passes the writing head.

=It is another object of the present invention to provide a first drive roller that acts in substantially the manner of a capstan to cause the sheet to slip over its surface when there is slack between the sheet roll and the first drive roller and to tightly adhere to the sheet and drive it when the sheet is held to the surface of the first drive roller under slight tension in the sheet.

It is a further object of the present invention to provide a sheet drive mechanism wherein the sheet is drawn from the roll by a first drive roller to respond to slippage and a second drive roller draws the sheet past the Writing head in cooperation with an idler roller.

It is still another object of the present invention to have a sheet drive mechanism for drawing a sheet at the face sides and not along the entire width of the sheet, to prevent tearing and pile-up under the writing head and to make the driving Iforce at each side of the sheet faces adjustable.

Other objects and advantages of the invention, not at the time enumerated, will become more readily apparent as the nature of the invention is better understood.

In the accompanying drawing, forming a part of this specification, the figures represented are as follows:

FIG. 1 is a partial schematic view in elevation of one embodiment of the invention, showing the sheet dispenser,

ice

a partial cross-sectional view of the sheet drive mechanism, land the paper take-up unit.

FIG. 2 is an elevation view along the line 2 2 of FIG. 1, showing one embodiment of the idler tension spring assembly of the invention.

FIG. 3 is a planned view of the paper drive mechanism taken along the line 3 3 of FIG. 1, portions of the apparatus being removed to aid in showing other details of one embodiment of the invention.

FIG. 4 is a partial section view taken in elevation along the line 4 4 of FIG. 3.

FIG. 5 is a side elevation view of the paper drive mechanism taken along the line 5 5 of FIG. 3.

FIG. 6 is a partial section View in elevation taken along the line 6 6 of FIG. 3 and showing one embodiment of the idler roller of the invention.

FIG. 7 is a partial section view in elevation along the line 7 7 of FIG. 3 and showing one embodiment of the primary drive roller of the invention.

FIG. 8 is a partial section view in elevation along the line 8 8 of FIG. 3 and showing one embodiment of the roller of the invention.

FIG. 9 fis a partial section View in elevation of another embodiment of the paper drive mechanism of the invention.

A preferred embodiment of the invention is shown by the Way of example in the drawings. Referring to FG. l, the apparatus generally comprises a sheet dispenser 1, sheet drive mechanism 2, and paper take-up unit 3. The paper dispenser 1 contains a sheet roll 3, such as paper or the like, and sheet 4 is drawn from the sheet dispenser 1 over a guide 5 by the primary drive roller 6 in the sheet drive mechanism 2. After the sheet 4 leaves the primary ldrive roller 6, the secondary drive roller 11 in cooperation 'With idler roller 12 draws the sheet 4 around roller 7, over the recording table 8, and under the pen 9 of galvanometer 10. The sheet 4 leaves the sheet drive mechanism 2 and travels to the take-up unit 3 where it is collected in a roll 13 by a suitable winding arrangement (not shown). As the sheet 4 is drawn past the pen 9, an electrical signal applied to terminals 14 of the galvanometer 10 moves the pin laterally across the recording sheet 4. In this manner, the electrical signal is recorded on the sheet 4 with the length of the sheet representing time and the displacement in a lateral direction of the sheet representing the amplitude of the electrical signal.

The paper dispenser 1 positions the sheet roll 3 lfor rotational 'movement as the sheet 4 is Withdrawn by the sheet drive mechanism Z. The roll 3 rotates about an axial shaft 15 disposed in slots 16 of mounting brackets 17 (only one of the two mounting brackets is shown). The brackets 17 are mounted vertically from a base plate 13 at each side of the roll and servie to space the roll from the base and permit -free rotational movement as the sheet 4 is withdrawn.

Provision is made to retard the movement of the roll 3, in effect braking the roll and furnishing a tension in the sheet as it leaves the roll 3. Many arrangements can be used to furnish the retarding force. FIG. l illustrates one preferred embodiment, wherein radial force is apL plied against the roll 3 by a brake arm assembly 18 disposed adjacent the roll 3 land mounted for pivotal movement on the shaft 19 between mounting blocks 20 (only one mounting block is shown) secured to the base 13.

The brake arm assembly has a roller 21 mounted for rotational movement on a shaft 22. Shaft 22 is iixed at one end to an arm 23, the other end of the arm 23 being positioned to rotate about the shaft 19. The radial force applied against the roll 3 is sustained by a spring 24 connected between the arm 23, near the end carrying the roller 21 and a lug 25 fastened at the opposite end of the base 13 from mounting block 20. The spring 24 pulls the brake arm assembly 18 against the roll 3 as the diameter of the roll diminishes, keeping a continuous retard' ing force against the roll 3. The brake arm serves to prevent the roll 3 from raveling after the sheet drive mechanism 2 stops. Also, since new rolls of sheet may be of different size and the spools on which the sheet is wound may vary from one roll to the next, the brake arm assembly 18 compensates to some extent for any unbalance in the roll 3 that would create slack and tension alternately as the sheet 4 is withdrawn.

The sheet drive mechanism 2 conveniently comprises side walls 26 and 27 and end walls 28 and 29. The top of the housing is covered by a plate 30 and a rib 31 is secured under the top plate 30 by means of suitable fasteners, such as by screws 32. The rib 31 extends laterally across the sheet 4 as it leaves the sheet drive mechanism 2. End wall 29 is cut away at the top portion to permit exit of the sheet 4 as it travels to the take-up unit 3.

Sheet 4 is withdrawn from roll 3 by primary drive roller 6 and passes around a guide 5. Guide 5, referring to FIGS. 1 and 3, is a rod mounted between the side walls 26 and 27. The mid-section of guide 5 has a smaller diameter than the end portions 40 over a length suflicient to compass the lateral dimension of sheet 4. The sheet 4 passes between the end portions 40 and the sheet 4 is thereby aligned for presentment to the primary drive roller 6. In this manner, there is substantially no lateral movement of the sheet and, as will be mentioned hereinafter, the guide is positioned to form the sheet 4 around the primary drive roller 6, over a substantial surface area.

The primary drive roller 6, referring to FIGS. 1 and 7, comprise an axial shaft 46 mounted for rotational movement in bearings 47 in side walls 26 and 27. The axis of shaft 46 is parallel to the axis of guide 5 and disposed substantially in the same plane. Shaft 46 extends outward from the side wall 27 and is removably secured in bearings 48, fastened in mounting block 49 by a collar 50 disposed at the far end of shaft 46 and held in place by set screw 51. On the inside of side wall 27 is a spurgear 52 which is fastened to the shaft 46 for rotational movement therewith by a set screw 53.

As the sheet 4 passes around the guide 5 the uniform, cylindrical surface 54 of the primary drive roller 6 is encompassed by the sheet 4 over more than 180 degrees of its surface. The relative arrangement of the guide 5 and primary drive roller 6 is such that the sheet 4 moves from the guide 5 in one direction around the primary drive roller 6 and leaves in substantially the opposite direction from the primary drive roller 6. Other relative positioning of the guide 5 and primary drive roller 6 can be used to achieve the substantial loop around the surface 54. In some arrangements the guide 5 can be eliminated and the sheet drawn directly from the roll 3 and formed around a substantial portion of surface 54 by a suitable guide means as the sheet leaves the primary drive roller 6.

The surface 54 of the primary drive roller 6 is made of a material with particular characteristics. First, the surface 54 provides maximum traction with the sheet 4 when in contact under a slight tautness about the primary drive roller 6. As previously mentioned, the arrangement of the guide 5 and the direction of withdrawal of the sheet 4 from the primary drive roller 6 is suitable to form a partial loop about the primary drive roller 6 to insure that when sheet 4 is taut a substantial part of surface 54 will contact the sheet 4. The material forming the surface 54 of the primary drive roller 6 also has the characteristic of being smooth and slick enough to allow for maximum slippage when there is no tension in the sheet.

A number of materials can be used for the surface 54. Materials that have been found highly effective are the vinyl compounds, generally known by the trademark,

Tygon, The properties of Tygon that make it such an outstanding drive surface are the natural adhesions, in the nature of attraction, exhibited by the material to smooth surfaces when held under mild pressure and the smooth surface character that permits immediate slippage when the pressure is reduced. Rubber or plastics may be used for the surface 54, but these materials do not offer the same type of smooth operation as achieved with the vinyl compounds, Tygon. The natural attraction of the vinyl compounds, Tygon, to a smooth surface greatly enhances the consistent tractive contact of the drive roller 6 and effective slippage when the contact pressure is reduced.

With surface 54 having the aforementioned characteristics, the primary drive roller 6 will continue to draw sheet 4 from the roll 3 as long as a slight tautness 1s maintained in sheet 4 from the roll 3. The brake arm assembly 1S acting to provide the retarding force at the roll end of sheet 4. If slack should occur between the roll 3 and the primary drive roller 6, the sheet 4 will slip on the primary drive shaft surface 54 until the slack has been taken up. In this manner, primary drive roller acts substantially as a capstan in feeding sheet 4 to successive parts of the drive mechanism 2 at a substantially uniform rate, irrespective of the occurrence of slack. It is apparent that the brake arm assembly coacts with the primary drive roller 6 to provide the degree of tautness required for the primary drive roller 6 to maintain a constant drive or, in the case of lack of tension to cause the sheet 4 to slip on the primary drive roller surface 54 until the slack is taken up.

After leaving the primary drive roller 6, the sheet 4 may pass directly to the point where a suitable writing instrument is located. In the illustrated preferred embodiment, the sheet 4 leaves the primary drive roller 6 and changes direction by passing over roller 7 and then over the recording table 8.

The roller 7, referring to FIGS. l and 8, comprises a shaft 60 fixed in the side walls 26 and 27 by means of screws 6l and a tubular member 63 is disposed axially on the shaft for rotational movement in end bearings 62. The axis of shaft 60 is disposed parallel to the axes of the guide 5 and primary drive roller 6 and located above and on the opposite side of the guide 5 from the primary drive roller 6. A substantial portion of surface 54 of the primary drive roller 6 is substantially encompassed as the sheet 4 passes under and around guide S, under and around primary drive roller 6, and under and around roller 7. The sheet 4 leaves the roller in substantially the opposite direction from the direction of movement of sheet 4 towards the roller 7.

The movement of the sheet 4 over the recording table 8 may be accomplished by a drawing force applied over the lateral surface of sheet 4. The sheet 4 can pass between the surfaces of a secondary drive roller and idler roller resiliently biased with respect to each other to receive the drawing force. In one such arrangement, the surfaces of the idler roller 12 and secondary drive roller 11 can contact the sheet 4 over the entire lateral surface of the sheet. It has been found, however, that after a period of use the sheet does not receive a uniform drawing force across its lateral surface, due to uneven wear in the parts, and the sheet tears or ruilies up. To overcome this diiculty the sheet 4 can receive a drawing force only at the sides of the sheet faces and this force can be adjustable at each side to provide an even pull even if the mechanism has been in use for a long time. Two embodiments for imparting the drawing force to a sheet are shown for illustrative purposes.

Referring to FIG. 4 for a detail showing of the secondary drive roller Il, the secondary drive roller 11 comprises a shaft 66 mounted for rotational movement in the side walls 26 and 27 by bearings 67. The axis of the secondary drive roller Ill is parallel to the axis of the guide 5, primary drive roller 6, and roller 7 and positioned over the primary drive roller 6 and on the opposite side from the guide and the roller 7 with respect to the primary drive roller 6. The diameter of surface 68 is the same along its length, presenting an even surface to sheet 4. The secondary drive roller 11 has a surface 68 that provides positive traction with the sheet 4, such as by knurling the surface, or using a material having suitable positive traction characteristic. The diameter of surface 68 is the same along its length presenting an even surface to sheet 4.

Primary drive roller 6 and secondary drive roller 11 are driven for rotational movement by motor 70. Shaft 66 of the secondary drive roller 11 has a spur-gear 69 fixed thereto by set screw 71. Spur-gear 69 meshes with spur-gear 52 to rotate primary drive roller 6 When shaft 66 is rotated. Shaft 66 extends outward from side 27 and is coupled through bevel gears 67 to motor 70. The rotational speeds of the primary drive roller 6 and the secondary drive roller 11 are made the same by the use of identical spur-gears 52 and 69. The periphery speeds of the two drive rollers are held substantially the same by appropriate dimensioning so that the sheet 4 is drawn at substantially the same speed by each of the drive rollers.

Combined with the secondary drive roller 11 is an idler roller 12, shown in FIG. 6. The idler roller 12 comprises a shaft 76 and a tubular member 77 axially disposed on the shaft 76 for rotational movement about bearings '78. The tubular member 77 is positioned axially along the shaft 76 by means of collars 79 fastened to the shaft 76 by set screws 80. The ends of tubular member 7'7 have opposite end portions 81 that have a greater diameter than the central portion 82. The length of the idler roller 12 is suflicient to overlie the complete lateral dimension of the sheet 4 with the ends 81 disposed over the central area of the sheet 4. Due to the arrangement of the surfaces contacting the sheet 4, the driving force is applied thereto only at the sides of the sheet faces. When the secondary drive roller 11 and idler roller 12 are held under moderate pressure against sheet 4 the end portions 81 of idler roller 12 contact the sheet 4 and provide drawing force but mid-section 82 does not, since it has a smaller diameter.

Each end of idler roller 76 is fastened by means of a screw S3 to a pivot arm 84 disposed outside the side wall and pivotally mounted at the opposite end to the respective side wall by means of screw 85, as best shown in FIGS. 5 and 8. Each pivot arm extends away from the pivot point, past the idler connection and curls loosely around the respective side wall and bends inwardly along the innerface of the side wall to form a lip 86 extending inwards towards the idler roller 12 as best shown in FIGS. l and 2. The pivot arms 84 permit movement of the idler shaft '76 in an opening 87 in each side wall disposed opposite the axial ends of the idler shaft 76. The idler roller 12 can thereby move with respect to the secondary roller 11 by rotation of the pivot arms 84.

The idler roller 12 can be resiliently biased against the sheet 4 by numerous arrangements Where the drive force is applied at the sides of the sheet faces it is preferable to have independent biasing adjustment for each side, thereby permitting an adjustment of the surfaces as the parts wear. An even pull on the sheet 4 is more easily achieved in this manner.

0ne illustrative embodiment of a suitable resilient biasing for the idler roller 12 is shown in FIGS. 1 and 2. The idler roller 12 is resiliently biased against the secondary drive roller 11 by means of a tension spring assembly 91 acting on pivot arms 84. The force is supplied by a leaf spring 92 fastened at its mid-section by means of screw 93 to the underside of rib 31. The arms of spring 92 extend between the sides 26 and 27 and projects over the lips 86 of the pivot arms 84. Adjustable screws 94 are threaded in and extended through the top Wall 30 and rib 31 to engage the upper surface of the leaf spring 92 at the approximate mid-section between the ends and the secured central portion to force the projecting arms of the leaf spring against the lips 86. The idler roller 12 is thereby held in a resilient manner against the sheet 4 and adjustment of the screw 94 controls the tension at one end of the idler roller 12 and, consequently, the drawing force applies to the side of the sheet. Changes in the dimensions of the parts due to wear can be compensated for by the independent adjustment of the tension at the ends of the idler roller 12 to maintain a uniform and even withdrawal force on the sheet 4.

Another arrangement of the idler roller and secondary drive roller is shown in FIG. 9, wherein like parts are identified by the same reference numerals as in the other figures. The axis of the secondary drive roller 104 is disposed above the level of the recording table 8. The secondary drive roller 104 has end portions 107 at opposite ends (only one is shown) having a greater diameter than the mid-portion 108. The underside of end portions 107 contacts the side faces of the sheet 4, while the rnid-portion 108 is not of suicient diameter to contact the sheet 4. Chain 106 couples the primary drive roller 6 and the secondary drive roller 11 for unied rotational movement. A motor (not shown) is coupled to the secondary drive roller 11 and rotates the drive rollers at a constant speed.

The idler roller is disposed adjacent the secondary drive roller 104 and comprises a tubular member of uniform diameter having an axis parallel to the action of the secondary drive roller 104 and mounted for rotational movement on a shaft 101. Each end of the shaft 101 is fastened to arm 102 and disposed to pivot about a pin 103 secured in the respective walls intermediate the end of the wall where the tension spring assembly 91 is located. The tension spring assembly 91 acts to force the end of the arm 102 opposite the idler roller 100 downward and correspondingly moves the idler roller 101 against the secondary drive roller 104. The sheet 4 passes between the idler roller 100 and the secondary drive roller 104 and onward` to the take-up unit 3.

In the embodiment of FIG. 9, as in the other illustrative embodiment, the positive driving force applied to the sheet 4 is at the sides of the sheet faces and the midportion of the sheet 4 does not contact the surface of the secondary drive roller. Variation between the idler roller 100 and the secondary drive roller 104 is obtained by adjusting the screws controlling the deployment of the leaf spring arms 92. Wear in the parts can be compensated for by the appropriate control of the tension between the idler roller 100 and the secondary drive roller 104.

It is apparent that the present invention has the advantages of compensating for the effect of slack delivered from the sheet roll without unduly interfering with the uniform passage of a recording sheet under the pin and, in addition, maintaining a uniform pull on the sheet as it passes under the pin. The variable adjustment of the driving force at the sides of the sheet faces helps to prolong the length of the device and make it more suitable for general use in many individual industrial applications.

While two embodiments of the invention have been described in detail, it must be recognized that variations in the specific mechanical parts and the arrangements are fully within the scope of the disclosed invention and the embodiments are not to be taken in any way to limit the scope of the invention. The appropriate limits and bounds for the disclosed invention are set forth in the claims attached to and forming a part of this specification.

What is claimed is:

l. An apparatus for adjusting the drive tension in a sheet drive mechanism; comprising,

a drive roller having a surface for traction with a sheet;

means for rotating said drive roller;

an idler roller havign an axis parallel to the axis of said drive roller;

a support member;

support arms pivotally attached to said support member parallel to each other;

said idler roller being rotatably supported from said arms;

a leaf spring;

means holding the center of said leaf spring stationary;

adjustable means for each arm of said leaf spring forcing the leaf spring arm into engagement with a different one of said arms supporting the idler, to resiliently bias said idler roller against the drive roller and permit separate adjustment of the tension between each end of the idler shaft and the drive shaft.

2. Apparatus for driving a recording sheet, comprising,

a holder for a recording sheet roll arranged to permit rotational movement of a recording sheet roll as the sheet is withdrawn;

means retarding the rotation of the roll as the sheet is withdrawn;

a first drive means for withdrawing the sheet from the roll and having a cylindrical surface of tractive character to drive the sheet when the sheet is taut and held rmly against said surface and smooth to the sheet to have maximum slippage about said surface when said sheet is not taut;

a second drive means including a roller and idler for drawing the sheet after the sheet passes at least partially around said surface of said first drive means;

means for supporting said roller and said idler on opposite faces of said sheet and in resilient contact with the sheet,

the surface of said roller and idler contacting said sheet only at the sides of said sheet faces, so that positive drive contact occurs only at the sides of the sheet faces;

yieldable means disposed at each end of said idler,

resiliently biasing said idler and roller together;

an adjustable means associated with each of said yieldable means and arranged to separately set the contact pressure of said idler and roller with the sheet at each side of the sheet faces; and,

the apparatus having means to record on the sheet between said iirst and second drive means.

3. Apparatus for driving a recording sheet, comprising,

a. holder for a recording sheet roll aranged to permit rotational movement of a recording sheet roll as the sheet is withdrawn;

means retarding the rotation of the roll as the sheet is withdrawn;

a rst drive means for withdrawing the sheet from the roll and having a cylindrical surface of tractive character to drive the sheet when the sheet is taut and held firmly against said surface and smooth to 8 the sheet to have maximum slippage about said surface when said sheet is not taut;

a second drive means including a roller and idler for driving the sheet after the sheet passes at least partially around said surface of said first drive means;

said idler having an axis parallel to the axis of said roller and being rotatably supported from two arms;

a support;

a spring means having first and second ends,

said spring means being mounted on said support; adjustable means extending from said support to force each end of said spring means in contact with one of said arms, to provide a separately adjustable resilient bias for each arm, forcing said idler and roller into contact wtih said sheet; and,

the apparatus having means to record on the sheet between said first and second drive means.

4. Apparatus for driving a recording sheet, comprising,

a holder for a recording sheet roll arranged to permit rotational movement of a recording sheet roll as the sheet is withdrawn;

means retarding the rotation of the roll as the sheet is withdrawn;

a first drive means for withdrawing the sheet from the roll and having a cylindrical surface of tractive character to drive the sheet when the sheet is taut and held irmly against said surface and smooth to the sheet to have maximum slippage about said surface when said sheet is not taut;

a second drive means including a roller and idler for driving the sheet after the sheet passes at least partially around said surface of said first drive means,

said idler having an axis parallel to the axis of said roller and being rotatably supported from two arms; a U-shaped support; each of said arms being pivotally mounted from a different leg of said U-support; a leaf spring,

the center of the leaf spring being fastened to the base of said U-support; adjustable means extending from the base of said U- support to force each end of the spring in contact with one of said arms, to provide a separately adjustable resilient bias for each arm; and, the apparatus having means to record on the sheet between said rst and second drive means.

Duffy Apr. 10, 1945 Brown et al Sept. 3, 1957 

2. APPARATUS FOR DRIVING A RECORDING SHEET, COMPRISING, A HOLDER FOR A RECORDING SHEET ROLL ARRANGED TO PERMIT ROTATIONAL MOVEMENT OF A RECORDING SHEET ROLL AS THE SHEET IS WITHDRAWN; MEANS RETARDING THE ROTATION OF THE ROLL AS THE SHEET IS WITHDRAWN; A FIRST DRIVE MEANS FOR WITHDRAWING THE SHEET FROM THE ROLL AND HAVING A CYLINDRICAL SURFACE OF TRACTIVE CHARACTER TO DRIVE THE SHEET WHEN THE SHEET IS TAUT AND HELD FIRMLY AGAINST SAID SURFACE AND SMOOTH TO THE SHEET TO HAVE MAXIMUM SLIPPAGE ABOUT SAID SURFACE WHEN SAID SHEET IS NOT TAUT; A SECOND DRIVE MEANS INCLUDING A ROLLER AND IDLER FOR DRAWING THE SHEET AFTER THE SHEET PASSES AT LEAST PARTIALLY AROUND SAID SURFACE OF SAID FIRST DRIVE MEANS; 